Abstract: GEANT4 (GEometry ANd Tracking) is an object-oriented Monte Carlo simulation toolkit to simulate the passage of particles through matter. This research was carried out to model a system for measuring positron lifetime in materials by GEANT4 whereby the nature of positron annihilation in material was understood clearly. The specific details of 22Na source which emitted positrons with its energy in a 0-545 keV range was reproduced by GEANT4. Based on the positron annihilation in the sample, the penetration and the lifetime of positron were investigated. Besides, the experimental measurements of the lifetime positron in some metals, such as Cu, Al, Fe and Ni, were also conducted at Center for Nuclear Techniques. After all, the GEANT4 simulation results have been compared to that of experiments. The results show that the positron energy distribution of 22Na source in GEANT4 is compatible with the published articles. The positron penetration in the samples, in simulation and experiment, have also the same results. The spectrum form of the positron lifetime in Cu, Al, Fe and Ni simulated in GEANT4 have a remarkable agreement with those of measured results. The system measuring directly positron lifetime, which has been simulated successfully, shows that using GEANT4 to evaluate the differences between experiment and theory of positron annihilation is essential for the material science field in particular and the physics in general.
Key words: positron annihilation, GEANT4.
